The present invention generally relates to capsules for containing beverage ingredients to a beverage producing system for use in connection with such capsules as well as to methods for producing such capsules.
The background of the present invention is the field of capsules which contain beverage ingredients (e.g., coffee ground, milk powder) or other comestible ingredients (e.g. dehydrated soup). By means of an interaction of these ingredients with a liquid, a beverage or other comestibles can be produced. The interaction can be for example an extraction, brewing or dissolution process. Such a capsule is particularly adapted to contain ground coffee in order to produce a coffee beverage by having hot water under pressure enter the capsule and draining a coffee beverage from the capsule.
Systems and methods for obtaining fluid comestibles from substances containing capsules are for example known from EP-A-512470.
The general principle of this extraction process can be summarized as follows:                An initially closed capsule is inserted between capsule holder means which are closed in a watertight manner about the capsule;        Water injection means of the machine inject water in the capsule;        Water interacts with the ingredients contained in the capsule while traversing the interior of the capsule and is then made to leave the capsule through at least one opening/perforation created in the second wall.        
The ingredients in the capsule constitute the “bottleneck” of the flow path of the water and will therefore cause a pressure drop between the upstream and the downstream side of the liquid flow through the capsule, which pressure drop will even increase during the interaction between the liquid and the ingredients for example due to a swelling of the ingredients. Correspondingly it has to be assured that the only water flow is actually taking place through the interior of the capsule and that no water can flow from the water injector. In other words, any water flow exterior to the capsule has to be stopped by a sealing engagement being positioned between the annular enclosing member of the holder means and the capsule and in the flow path between the water injector and the beverage-draining bore.
Such sealing engagement can be achieved at least to a certain degree by the pinching engagement between the capsule holder means (i.e., annular enclosing member and capsule holder) and the flange-like rim of the body inbetween.
In case the sealing engagement is not working properly and water is flowing outside the capsule, no pressure sufficient to cause the tearing of the tear face will be built up inside the capsule or, alternatively, the pressure will be causing no complete tearing of the tear face and therefore a poor extraction of the substance. In such a scenario water will be drained from the beverage production device without having interacted or fully interacted under sufficient pressure conditions, with the ingredients contained in the capsule.
An improvement could be thought of according to which this sealing engagement is further improved by lining the inner wall of the annular member with a rubber-elastic material. In other words, according to said approach the sealing engagement is assured by structures fixed to or attached with the beverage-producing device. This has disadvantages in that after the use of a substantial number of capsules a wearing off of the fixed sealing means can take place such that the quality of the produced beverage is increasingly deteriorated by water passing the no longer properly efficient sealing. Furthermore, the sealing means can become dirty with organic residues sticking to it which is not very hygienic and may affect the sealing and pressure conditions as well during extraction.
Any “leak” at the exterior of the capsule reduces the pressure build-up inside the capsule. On the other hand, it is well known that a sufficient extraction pressure is a key factor for the quality of espresso-style coffee.
European co-pending patent application No. 04025320.5 entitled “Capsule with sealing means” aims at an improvement of the sealing engagement positioned between the liquid inlet and the beverage draining side of such a beverage production system. The invention aims at transferring a resilient part of the sealing engagement from the beverage production device to the capsule. The advantage is that any resilient sealing member is only used once (i.e. only with the associated capsule) such that a proper functioning of the sealing can be assured and no hygienic problems can occur at the sealing member.
The present invention aims at another improvement of European co-pending patent application No. 04025320.5 in order to improve the sealing conditions between the capsule and the sealing member so to ensure watertightness during brewing. Indeed, it is of importance to avoid any potential liquid leakage between the sealing member and the rest of the capsule in particular by creating a good bond between the two.
Furthermore, it is also of importance that the sealing member is integrated to the capsule using a process that can be implemented on a large industrial scale, be highly reliable with minimal defective products and be also cost effective.